How severe is CVE-2021-22945?

CVE-2021-22945 has a CVSS 3.x base score of 9.1, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability high.

Is CVE-2021-22945 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 6% (93rd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-22945?

CVE-2021-22945 primarily affects Haxx Libcurl. In total, 19 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-22945?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2021-22945 published?

CVE-2021-22945 was published on 2021-09-23 and last updated on 2026-06-17.

CVE-2021-22945

CVE-2021-22945 is a critical-severity vulnerability in Haxx Libcurl with a CVSS 3.x base score of 9.1. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-415.

Key facts

Severity: Critical (CVSS 3.x base score 9.1)
CVSS v2: 5.8
EPSS exploit prediction: 6% (93rd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-415
Affected product: Haxx Libcurl
Published: 2021-09-23
Last modified: 2026-06-17

Description

When sending data to an MQTT server, libcurl <= 7.73.0 and 7.78.0 could in some circumstances erroneously keep a pointer to an already freed memory area and both use that again in a subsequent call to send data and also free it *again*.

Frequently asked questions

What is CVE-2021-22945?: When sending data to an MQTT server, libcurl <= 7.73.0 and 7.78.0 could in some circumstances erroneously keep a pointer to an already freed memory area and both use that again in a subsequent call to send data and also free it *again*.
How severe is CVE-2021-22945?: CVE-2021-22945 has a CVSS 3.x base score of 9.1, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability high.
Is CVE-2021-22945 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 6% (93rd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-22945?: CVE-2021-22945 primarily affects Haxx Libcurl. In total, 19 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-22945?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2021-22945 published?: CVE-2021-22945 was published on 2021-09-23 and last updated on 2026-06-17.

References

Affected products (19)

cpe:2.3:a:haxx:libcurl:*:*:*:*:*:*:*:*
cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:*
cpe:2.3:o:fedoraproject:fedora:35:*:*:*:*:*:*:*
cpe:2.3:a:netapp:cloud_backup:-:*:*:*:*:*:*:*
cpe:2.3:a:netapp:clustered_data_ontap:-:*:*:*:*:*:*:*
cpe:2.3:a:oracle:mysql_server:*:*:*:*:*:*:*:*
cpe:2.3:o:netapp:h300s_firmware:-:*:*:*:*:*:*:*
cpe:2.3:o:netapp:h500s_firmware:-:*:*:*:*:*:*:*
cpe:2.3:o:netapp:h700s_firmware:-:*:*:*:*:*:*:*
cpe:2.3:o:netapp:h300e_firmware:-:*:*:*:*:*:*:*
cpe:2.3:o:netapp:h500e_firmware:-:*:*:*:*:*:*:*
cpe:2.3:o:netapp:h700e_firmware:-:*:*:*:*:*:*:*
cpe:2.3:o:netapp:h410s_firmware:-:*:*:*:*:*:*:*
cpe:2.3:o:netapp:solidfire_baseboard_management_controller_firmware:-:*:*:*:*:*:*:*
cpe:2.3:o:apple:macos:*:*:*:*:*:*:*:*
cpe:2.3:a:siemens:sinec_ins:*:*:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:11.0:*:*:*:*:*:*:*
cpe:2.3:a:splunk:universal_forwarder:*:*:*:*:*:*:*:*
cpe:2.3:a:splunk:universal_forwarder:9.1.0:*:*:*:*:*:*:*

More vulnerabilities in Haxx Libcurl

CVE-2023-38545 — Critical (CVSS 9.8): This flaw makes curl overflow a heap based buffer in the SOCKS5 proxy handshake. When curl is asked to pass along the…
CVE-2019-3822 — Critical (CVSS 9.8): libcurl versions from 7.36.0 to before 7.64.0 are vulnerable to a stack-based buffer overflow. The function creating an…
CVE-2017-8818 — Critical (CVSS 9.8): curl and libcurl before 7.57.0 on 32-bit platforms allow attackers to cause a denial of service (out-of-bounds access…
CVE-2017-8817 — Critical (CVSS 9.8): The FTP wildcard function in curl and libcurl before 7.57.0 allows remote attackers to cause a denial of service…
CVE-2017-8816 — Critical (CVSS 9.8): The NTLM authentication feature in curl and libcurl before 7.57.0 on 32-bit platforms allows attackers to cause a…
CVE-2016-7167 — Critical (CVSS 9.8): Multiple integer overflows in the (1) curl_escape, (2) curl_easy_escape, (3) curl_unescape, and (4) curl_easy_unescape…

All CVEs affecting Haxx Libcurl →

Other CWE-415 (Double Free) vulnerabilities

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CVE-2026-8925 — Critical (CVSS 9.8): The curl logic that works with SASL authentication could end up cleaning up the GSASL context *twice* without clearing…
CVE-2020-37239 — Critical (CVSS 9.8): libbabl 0.1.62 contains a broken double free detection vulnerability that allows attackers to bypass memory safety…
CVE-2026-43011 — Critical (CVSS 9.8): In the Linux kernel, the following vulnerability has been resolved: net/x25: Fix potential double free of skb When…
CVE-2026-31609 — Critical (CVSS 9.8): In the Linux kernel, the following vulnerability has been resolved: smb: client: avoid double-free in…
CVE-2026-31608 — Critical (CVSS 9.8): In the Linux kernel, the following vulnerability has been resolved: smb: server: avoid double-free in…

Browse all CWE-415 (Double Free) vulnerabilities →